Tyre sensor device with flexible printed circuit board

ABSTRACT

A tyre sensor device having a container with a container housing and a tyre sensor device electronics assembly, the tyre sensor device electronics assembly including a foldable flexible printed circuit board with at least two printed circuit board portions each having two surfaces and being suitable for placement of electronic components of the tyre sensor device. The electronic components have at least one sensor for sensing at least one tyre parameter. The foldable flexible printed circuit board is configured to be folded for insertion of the tyre sensor device electronics assembly in the container housing. The container housing is adapted to contain the foldable printed circuit board in a folded condition.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 15/125,566 filed on Sep. 12, 2016 which is the U.S.National Stage of International Patent Application No. PCT/EP2015/056424filed on Mar. 25, 2015 which, in turn, claims priority to ItalianApplication No. MI2014A000532 filed on Mar. 28, 2014, the contents ofeach of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to the field of sensors for vehicle tyres,and particularly to a tyre sensor device.

Overview of the Related Art

The incorporation of electronic devices within pneumatic tyres is takinga greater importance in order to increase the safety of vehicles. Tyreelectronics may include sensors and other components suitable forobtaining information regarding the behavior of a tyre, as well asvarious physical parameters thereof, such as for example temperature,pressure, number of tyre revolutions, vehicle speed, etc.

Such information may become useful in tyre monitoring and/or alarmsystems.

Furthermore, active control/safety systems of the vehicle may be basedon information sent from sensor devices provided in the tyres.

Active safety systems use information about the external environment ofa vehicle to change the vehicle behavior in pre-crash time period orduring the crash event, with the ultimate goal of avoiding a crashaltogether. Initially, active safety systems were primarily focused onimproving the vehicle longitudinal motion dynamics, in particular, onmore effective braking Anti-lock Braking Systems (ABS) and TractionControl (TC) systems. TC systems prevent the wheel from slipping whileimproving vehicle stability and steerability by maximizing the tractiveand lateral forces between the vehicle's tyre and the road. Thesesystems were followed by more powerful vehicle stability controlsystems, e.g., Electronic Stability Program (ESP), Vehicle StabilityControl (VSC), and Dynamic Stability Control (DSC). These latter systemsuse both brakes and engine torque to stabilize the vehicle in extremehandling situations by controlling the yaw motion. Active suspensionsystems are also an important part in vehicle active safety systems.They have been traditionally designed by trading-off three conflictingcriteria: road holding, load carrying and passenger comfort. Thesuspension system has to support the vehicle, provide directionalcontrol during handling manoeuvres and provide effective isolation ofpassengers/payload from road disturbances.

The active safety control systems described above are based upon theestimation of vehicle dynamics variables such as forces, load transfer,tire-road friction. The more accurate and “real time” the parameterestimation, the better the overall performance of the control system.Currently, most of these variables are indirectly estimated usingon-board sensors, and are not very accurate. Using measurements made bysensors fitted on the vehicle tyres would provide far more accurateestimation of the parameters relevant to the vehicle dynamics.

SUMMARY OF THE INVENTION

Setting up a system based on sensors fitted on vehicle tyres is howevera challenging task, for several reasons. In particular, the tyre sensordevice should have limited dimensions and/or weight, in order to limitor possibly avoid unbalance of the tyre during rotation. However,complex tyre sensors adapted to provide detailed information to avehicle control system related to the behavior of the tyres duringrunning of a vehicle need a number of electronics and/or sensingcomponents which have to be provided. Such plurality of components canreach a number of a hundred or more and need space to be properlylocated. This goes against the requirement of having a tyre sensordevice being sufficiently small in dimensions.

The inventors have found that a very compact tyre sensor device can beaccomplished by exploiting a flexible printed circuit board. Inparticular, the flexible printed circuit board can host a high number ofcomponents and be folded in order to limit the occupied space.

According to an aspect of the present invention, a tyre sensor device isprovided, comprising a connecting element for connecting the tyre sensordevice to a vehicle tyre, and a tyre sensor device electronics assemblyhoused in the connecting element.

According to another aspect of the present invention, a vehicle tyrecomprising an inner liner is provided, wherein a tyre sensor device isconnected to said inner liner through a connecting element, said tyresensor device comprising a tyre sensor device electronics assemblyhoused in the connecting element.

Preferred aspects of the present invention are described hereinbelow.

The tyre sensor device electronics assembly comprises a flexible printedcircuit board being foldable and comprising at least two printed circuitboard portions, each having two surfaces, the at least two printedcircuit board portions being suitable for the placement, on at least onesurface thereof, of electronic components of the tyre sensor device,wherein said electronic components comprise at least one sensor forsensing at least one tyre parameter. The flexible printed circuit boardis folded so that the tyre sensor device electronics assembly can beinserted in the connecting element with the at least two printed circuitboard portions being essentially planar.

Preferably, the flexible printed circuit board is folded such that theat least two essentially planar printed circuit board portions lie onsubstantially vertically stacked planes.

The connecting element may comprise a rubber housing adapted to beattached to an inner liner of the tyre. The rubber housing preferablyhas a seat for receiving a container having a cavity for accommodatingthe tyre sensor device electronics assembly.

Preferably, the tyre sensor device comprises a housing, accommodated insaid container and adapted to contain the folded printed circuit board.

Said housing may comprise a first housing part and a second housing partjoinable to each other, and a cap that closes from above the housing.

Preferably, the flexible printed circuit board is foldable to a generic“S” or “Z” shape and, when folded, it comprises three essentially planarportions suitable for the placement, on at least one surface thereof, ofelectronic components of the tyre sensor device.

The flexible printed circuit board may comprise two joining portions forjoining the three essentially planar portions, said joining portionsensuring flexural mechanical connection between the essentially planarportions and electrical connection among the electronic componentsplaced on the essentially planar portions.

In embodiments of the present invention, the flexible printed circuitboard has three conductive layers for signals and one conductive layerfor a ground potential in the three essentially planar portions, and oneconductive layer for the signals and one conductive layer for the groundpotential in the joining portions.

The tyre sensor device may advantageously comprise a transmittingantenna that comprises an end portion of the flexible printed circuitboard, joined to the one of the essentially flat portions by an antennajoining portion.

Advantageously, the tyre sensor device may comprise contact terminalsfor interfacing the tyre sensor electronics assembly to an externalterminal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bemade evident by the following description of some exemplary andnon-limitative embodiments thereof, to be read in conjunction with theattached drawings, wherein:

FIG. 1 shows a tyre sensor device according to an embodiment of thepresent invention, in perspective;

FIG. 2 shows the tyre sensor device of FIG. 1 in exploded view;

FIG. 3 shows a casing of the tyre sensor device of FIGS. 1 and 2, inperspective;

FIG. 4 shows a cross section of the tyre sensor device casing of FIG. 3along a median vertical plane;

FIG. 5 shows a cross section of the tyre sensor device of FIG. 1 along amedian vertical plane;

FIG. 6 is a lateral view of the tyre sensor device componentsaccommodated within the tyre sensor device casing, with a partiallyfolded flexible Printed Circuit Board (PCB) with tyre sensor deviceelectronics to be accommodated inside the tyre sensor device casing;

FIG. 7 is a top plan view of the flexible PCB, in unfolded condition;

FIG. 8 is a side view of the flexible PCB of FIG. 7, in unfoldedcondition;

FIG. 9 is a bottom view of the flexible PCB of FIGS. 7 and 8, inunfolded condition;

FIG. 10 is a front view of the flexible PCB of FIGS. 7 to 9, in unfoldedcondition;

FIG. 11 is a schematic, functional block diagram of the tyre sensorelectronics; and

FIGS. 12A-12G show some steps of an exemplary assembly procedure of thetyre sensor device.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

Making reference to the drawings, in FIG. 1 there is shown, inperspective, a tyre sensor device 100 according to an embodiment of thepresent invention. The tyre sensor device 100 is also shown in explodedview in FIG. 2. The tyre sensor device 100 comprises a casing 205 foraccommodating tyre sensor device components, described later on indetail. The tyre sensor device casing 205 comprises a connecting part210 and a base container 215. The connecting part 210 is genericallycircular in shape and is intended to be attached to an inner liner of atyre (not shown in the drawings), so as to connect the tyre sensordevice 100 to the tyre. The connecting part 210 is for example made ofrubber. The connection between the sensor device 100 to the inner linerof the tyre may be for example accomplished by gluing.

The base container 215 is attached to the connecting part 210. Theconnecting part 210 has a circular collar 217 rising from a circularbase of the connecting part 210, the circular collar 217 being hollowfor receiving and accommodating therein at least a portion of the basecontainer 215.

The base container 215 is generically cylindrical and hollow so as todefine therein a cavity within which the tyre sensor device componentsare accommodated. As visible in FIG. 2, the tyre sensor devicecomponents that are accommodated in the cavity of the base container 215comprise: a bottom bumper 220 (optional); a power supply battery 225; anelectronics assembly 230, enclosed within a housing 235, and a clip 240for closing the base container 215, so as to keep the tyre sensor devicecomponents within the base container 215.

FIGS. 3 and 4 show the tyre sensor device casing 205 alone (i.e., withthe connecting part 210 and the base container 215, but without theother components shown in FIG. 2) in perspective (FIG. 3) and in crosssection along a median vertical plane (FIG. 4).

The connecting part 210 has a generically circular base flange 305having a first diameter, and, on an opposite side with respect to a baseflange side 405 that in use abuts the tyre inner liner, the connectingpart 210 restricts and rises (preferably, in a rounded and smoothmanner) to form the circular collar 217 which is hollow to form agenerically cylindrical seat 310 for receiving the base container 215.

The base container 215 has a portion that is received within the seat310 of the connecting part 210. The portion of the base container 215that is received within the seat 310 preferably has, e.g. two,projecting ribs 410, for example circumferential, for making theattachment of the base container 215 to the connecting part 210 firmer.The portion of the base container 215 that protrudes from the seat 310has two diametrically opposite, arc-shaped projecting walls 315.

FIG. 5 shows a cross section along a vertical median plane similar tothat of FIG. 4 of the tyre sensor device of FIG. 1, complete of all thecomponents. The constitution of the electronics assembly 230 within thehousing 235 is also visible, as well as two O-rings 505 advantageouslyprovided below the electronics assembly 230 (more precisely, between theelectronics assembly and the battery 225) and/or above it (moreprecisely, between the electronics assembly and the clip 240), tocounteract possible misalignment and/or friction between the electronicsassembly and the other components of the tyre sensor device.

The electronics assembly 230 comprises a flexible Printed Circuit Board(PCB) 510, with electronic components mounted thereon. In FIG. 5 theflexible PCB 510 is in the flexed and folded condition, whereas in FIG.6 the flexible PCB 510 is in a partially flexed, partially foldedcondition, while FIGS. 7, 8, 9 and 10 are, respectively, a top planview, a side view, a bottom view and a front view of the flexible PCB510 in an unflexed condition, with the components of the electronicsassembly being better visible. FIG. 11 is a schematic, functional blockdiagram of the tyre sensor device electronics assembly 230.

Hereinafter, the electronics assembly 230 is described referring jointlyto FIGS. 6 to 11.

The electronics assembly 230 comprises a transmitting antenna 1105 (e.g.a transmitting antenna adapted for Ultra Wide Band (UWB) transmission)for transmitting (uplink channel) to a receiver (not shown), e.g. acoordinator device for coordinating two or more tyre sensor devicesinstalled on two or more tyres of a vehicle.

An antenna for a downlink channel may optionally be provided, i.e. forreceiving from the coordinator device. For example, the receivingantenna can be a Low Frequency (LF) antenna 1110; as an alternative, thetransmitting antenna 1105 might be exploited also as a receivingantenna.

The transmitting antenna is fed by a signal acquisition, processing andtransmission unit 1115, e.g. an ASIC (Application Specific IntegratedCircuit).

The receiving antenna 1110 feeds a receiver unit 1120 (e.g. an LFreceiver unit), that in turn feeds the signal acquisition, processingand transmission unit 1115.

The receiver 1120 and the signal acquisition, processing andtransmission unit 1115 are interfaced with one or more tyre sensor units1125, adapted to sense at least one tyre parameter, comprising forexample a temperature sensor, and/or an accelerometer sensor, and/or apressure sensor, and with memory units 1130.

A power supply unit 1135 supplies power to the various units of theelectronics assembly 230. The power is supplied either by the battery225, or by an external power source 1140. The power from the externalpower source 1140 is for example received through contact terminals 605in the form of pillars that, when the flexible PCB 510 is flexed andhoused in the housing 235, extends vertically. The contact terminals 605may also be also used for interfacing the electronics assembly 230 withan external equipment—not shown—e.g. for programming/re-programming thesensor.

The electronics assembly 230 can typically comprise further components,like resistors, capacitors, diodes, transistors, mounted to the flexiblePCB 510. Such components are not described in detail since theirprovision and arrangement is routinary work for the average designer ofelectronics systems.

The flexible PCB 510, as visible in FIGS. 7 to 9, comprises three mainPCB portions 705, 710, 715, joined by joining PCB portions 720, 725. Themain PCB portions 705, 710, 715 have a generically circular shape (othershapes being however possible; e.g., the shape of the main PCB portionsmay depend on the shape of the housing 235) and are larger than thejoining PCB portions 720, 725, which for example are genericallyrectangular. The electronic components are mounted to the main PCBportions 705, 710, 715 of the flexible PCB, preferably on both sidesthereof. The joining PCB portions 720, 725 ensure flexural mechanicalconnection between the main portions, as well as electrical connectionamong the electronic components. The transmitting antenna 1105 is forexample a strip antenna, formed e.g. by screen printing on a genericallyrectangular end portion 735 of the flexible PCB 510, joined to the mainPCB portion 705 by a joining portion 730. The end portion 735 where thetransmitting antenna is formed is flexible as the rest of the PCB 510,so that it can be bent to take an arc shape, as visible in FIG. 6.

The housing 235 for the electronics assembly 230 comprises two parts 610and 615 that are joinable to each other and which encase and support theflexible PCB 510, and a cap 245 that closes from above the housing 235.In particular, the part 610 (closer part) of the housing 235 is shapedso to have an arc-shaped shoulder that is used as a support for the endportion 735 of the flexible PCB 510, forming the transmitting antenna1105. When joined to each other, the two parts 610 and 615 of thehousing 235 form a solid and compact assembly which can be insertedwithin the base container 215, possibly after having been protected bythe cap 245.

Under the end portion 735 a magnetic shield is preferably provided, forshielding the transmitting antenna 1105 from the remaining electronics.

The flexible PCB 510 is for example realized to have four layers in themain portions (three conductive layers for the signals and oneconductive layer for the ground), and two layers (one conductive layerfor the signals and one conductive layer for the ground) in the joiningportions.

In particular, the flexible PCB 510 may be an assembly of multiplelayers composed of:

-   -   polymide and adhesive for the non conductive layers;    -   copper for the internal conductive layers;    -   copper, nickel and gold for the external conductive layers.

Preferably, a solder mask is used to protect the PCB on the externallayer.

The flexible PCB 510, with the electronic components mounted thereto, isfolded, for example to an “S” or “Z” shape as mentioned in theforegoing, with the main PCB portions 705, 710, 715 (where theelectronic components are mounted) which remain essentially planar whenthe flexible PCB 510 is folded, lying in three parallel planes. Thecapability to be folded is made possible by the flexibility of thejoining PCB portions 720, 725, as well as by the flexible materialmaking the PCB 510.

By providing a flexible PCB 510 that is foldable to an “S” or “Z” shape,up to six essentially flat PCB surface portions are made available forthe placement of electronic components (the three main PCB portions 705,710, 715, each having two sides). In other embodiments of the presentinvention, the flexible PCB 510 is folded to, e.g., a “C” shape (inwhich case, four essentially flat PCB surface portions are madeavailable for the placement of electronic components), or to other, morecomplex shapes, making available more than six essentially flat PCBsurface portions for the placement of electronic components.

When folded, the flexible PCB 510 is encased in the closer 235.

Some steps of an exemplary assembly procedure of the sensor node 100 aredepicted in FIGS. 12A-12G.

As shown in FIG. 12A, the flexible PCB 510 with the electroniccomponents already mounted thereto is laid down, in un-flexed condition,on an assembling tool 1205 that is suitably shaped to receive theflexible PCB 510. The assembling tool 1205 comprises a holding plate1210 that, after the flexible PCB 510 is laid down in proper position onthe mounting tool 1205, is screwed to the assembling tool 1205 forholding the flexible PCB 510 in position during the subsequentoperations (FIG. 12B).

Then, the end portion 735 of the flexible PCB 510 that forms thetransmitting antenna 1105 is then bent to take an arc shape (FIG. 12C).

The flexible PCB 510 is then removed from the mounting tool 1205.

The flexible PCB 510 is bent, as in FIG. 12D, to the compactconfiguration shown in FIG. 12E.

Finally, the bent PCB is inserted into the housing 235 closed by the cap245 (FIG. 12F), and the assembly is preferably potted.

Thanks to the present invention, a small but complex sensor device canbe built: For example, the sensor device can include more than 100 SMD(Surface Mount Device) components plus 2 plastic tube, 4 contact pinsand 2 battery contacts, all embedded in a housing 235 having a diameterlower than 2 cm and a thickness of about 1-1.5 cm.

The invention claimed is:
 1. A tyre sensor device comprising a containerhaving a container housing, and a tyre sensor device electronicsassembly, the tyre sensor device electronics assembly comprising: afoldable flexible printed circuit board comprising at least two printedcircuit board portions each having two surfaces, the at least twoprinted circuit board portions being suitable for placement, on at leastone surface thereof, of electronic components of the tyre sensor device,the electronic components comprising at least one sensor for sensing atleast one tyre parameter, the foldable flexible printed circuit boardbeing configured to be folded for insertion of the tyre sensor deviceelectronics assembly in the container housing, the container housingbeing adapted to contain the foldable printed circuit board in a foldedcondition.
 2. The tyre sensor device of claim 1, further comprising aconnecting element for connecting the tyre sensor device to a vehicletyre.
 3. The tyre sensor device of claim 2, wherein the connectingelement comprises a rubber housing adapted to be attached to an innerliner of the tyre.
 4. The tyre sensor device of claim 3, wherein therubber housing has a seat for receiving said container.
 5. The tyresensor device according to claim 1, wherein the container housingcomprises a first container housing part and a second container housingpart joinable to each other.
 6. The tyre sensor device according toclaim 1, wherein the foldable flexible printed circuit board is foldableto a generic “S” or “Z” shape and, when folded, comprises threeessentially planar portions suitable for the placement, on at least onesurface thereof, of electronic components of the tyre sensor device. 7.The tyre sensor device according to claim 6, wherein the foldableflexible printed circuit board comprises two joining portions forjoining the three essentially planar portions.
 8. The tyre sensor deviceaccording to claim 7, wherein the three essentially planar portionscomprise three conductive layers for signal conduction and oneconductive layer for a reference potential, and the joining portionscomprise one conductive layer for signal conduction and one conductivelayer for a reference potential.
 9. The tyre sensor device according toclaim 1, further comprising contact terminals for interfacing the tyresensor electronics assembly to an external terminal.
 10. A vehicle tyrecomprising an inner liner and the tyre sensor device of claim 1connected to the inner liner.